Carbon dioxide efflux in a rhodic hapludox as affected by tillage systems in southern Brazil

Abstract

SUMMARYAgricultural soils can act as a source or sink of atmospheric C, according to the soil management. This long-term experiment (22 years) was evaluated during 30 days in autumn, to quantify the effect of tillage systems (conventional tillage-CT and no-till-NT) on the soil CO 2 -C flux in a Rhodic Hapludox in Rio Grande do Sul State, Southern Brazil. A closed-dynamic system (Flux Chamber 6400-09, Licor) and a static system (alkali absorption) were used to measure soil CO 2 -C flux immediately after soybean harvest. Soil temperature and soil moisture were measured simultaneously with CO 2 -C flux, by Licor-6400 soil temperature probe and manual TDR, respectively. During the entire month, a CO 2 -C emission of less than 30 % of the C input through soybean crop residues was estimated. In the mean of a 30 day period, the CO 2 -C flux in NT soil was similar to CT, independent of the chamber type used for measurements. Differences in tillage systems with dynamic chamber were verified only in short term (daily evaluation), where NT had higher CO 2 -C flux than CT at the beginning of the evaluation period and lower flux at the end. The dynamic chamber was more efficient than the static chamber in capturing variations in CO 2 -C flux as a function of abiotic factors. In this chamber, the soil temperature and the water-filled pore space (WFPS), in the NT soil, explained 83 and 62 % of CO 2 -C flux, respectively. The Q 10 factor, which evaluates CO 2 -C flux dependence on soil temperature, was estimated as 3.93, suggesting a high sensitivity of the biological activity to changes in soil temperature during fall season. The CO 2 -C flux measured in a closed dynamic chamber was correlated with the static alkali adsorption chamber only in the NT system, although the values were underestimated in comparison to the other, particularly in the case of high flux values. At low soil temperature and WFPS conditions, soil tillage caused a limited increase in soil CO 2 -C flux.Index terms: no-till, greenhouse gases, soil temperature, soil moisture. RESUMO: EMISSÃO DE DIÓXIDO DE CARBONO EM LATOSSOLO VERMELHO ALTERADA POR SISTEMAS DE PREPARO NO SUL DO BRASILOs solos agrícolas podem atuar como dreno ou fonte de C atmosférico, dependendo do sistema de manejo adotado. Este estudo foi desenvolvido em experimento de longa duração (22 anos), durante o período de 30 dias do outono, com o objetivo de avaliar o impacto de sistemas de preparo de solo (preparo convencional-PC e plantio direto-PD) nas emissões de C-CO 2 de um Latossolo Vermelho distrófico, em Cruz Alta, RS. As emissões de C-CO 2 do solo foram avaliadas com câmaras dinâmica (Flux Chamber 6400-09, Licor) e estática (com captação em solução alcalina), imediatamente após a colheita da soja. A temperatura e a umidade do solo foram registradas, concomitantemente com as emissões de C-CO 2 , por meio de sensor de temperatura e TDR manual, respectivamente, integrantes do Licor-6400. Estimouse que, em 30 dias, uma quantidade equivalente a menos de 30 % do C aportado pelos resíduos de soj...

Long-term C-CO2 emissions and carbon crop residue mineralization in an oxisol under different tillage and crop rotation systems

“…However, periods with distinct patterns also occurred, e.g., between December 1999 and January 2000, when, even at high air temperatures, low C-CO 2 emissions were observed, probably related to low soil moisture (Figure 3). Air temperature, soil moisture and their interactions effects on soil C-CO 2 emissions have been frequently reported in the literature (Kucera & Kirkham, 1971;Franzluebbers et al, 1995;Mielnick, 1996;Moreira & Siqueira, 2002;Costa et al, 2008;Siqueira Neto et al (2009);Chavez et al, 2009). However, in this study, averaged across cropping systems, no significant correlation with soil moisture was observed in the C-CO 2 efflux from the tillage systems CT (r=0.135, p=0.097) and NT (r=0.011, p=0.89).…”

Soil CO2 emission as related to incorporation of sugarcane crop residues and aggregate breaking after rotary tiller

“…This result is corroborated by several short-term studies in which the emission is examined, showing that after soil preparation, carbon loss via CO 2 to the atmosphere also increases (LA SCALA et al, 2006). Emissions as high as several tons of CO 2 in a few weeks have been recorded in plots where tillage was conducted in addition to that portion without disturbance (CHAVEZ et al, 2009;LA SCALA et al, 2006).…”

Carbon stock and its compartments in a subtropical oxisol under long-term tillage and crop rotation systems

“…For this clayey oxidic soil, the increase in TOC was more influenced by the annual crop C input than by the tillage system (Figure 2). In the same experiment, Chavez et al (2009) found that the soil C-CO 2 emission peak induced by soil tillage had short duration and there was no difference between NT and CT in soil C-CO 2 efflux in a 30-day period. Also, Campos et al (in press) found similar soil C-CO 2 efflux values from NT and CT in a two-year period in the same experiment.…”